diff --git a/db/task_runtime_test.go b/db/task_runtime_test.go
new file mode 100644
index 0000000..492343f
--- /dev/null
+++ b/db/task_runtime_test.go
@@ -0,0 +1,172 @@
+package db
+
+import (
+	"database/sql"
+	"testing"
+)
+
+func TestTaskRunSegmentLifecycle(t *testing.T) {
+	d, err := Open(testDSN(t))
+	if err != nil {
+		t.Skipf("postgres unavailable (%v) — skipping", err)
+	}
+	defer d.Close()
+
+	task, err := d.CreateTask("runtime lifecycle", "runtime lifecycle test", nil, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = d.DeleteTask(task.ID) })
+
+	active, started, err := d.StartTaskRunSegment(task.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if started == nil {
+		t.Fatal("StartTaskRunSegment did not open a segment")
+	}
+	if active != 0 {
+		t.Fatalf("new task active seconds=%d, want 0", active)
+	}
+	if _, err := d.Exec(`UPDATE tasks SET run_segment_started_at=now()-interval '3 seconds' WHERE id=$1`, task.ID); err != nil {
+		t.Fatal(err)
+	}
+
+	active, started, err = d.FinalizeTaskRunSegment(task.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if active <= 0 || started != nil {
+		t.Fatalf("first finalize active=%d started=%v, want positive and NULL", active, started)
+	}
+	firstActive := active
+
+	// Pause folds the open segment exactly once and closes it. Repeated
+	// finalization after wall-clock advancement remains a no-op.
+	if _, _, err := d.StartTaskRunSegment(task.ID); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := d.Exec(`UPDATE tasks SET run_segment_started_at=now()-interval '3 seconds' WHERE id=$1`, task.ID); err != nil {
+		t.Fatal(err)
+	}
+	active, started, err = d.SetPausedRuntime(task.ID, true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if active <= firstActive || started != nil {
+		t.Fatalf("pause active=%d started=%v, want increase and NULL", active, started)
+	}
+	pausedActive := active
+	if active, started, err = d.FinalizeTaskRunSegment(task.ID); err != nil {
+		t.Fatal(err)
+	} else if active != pausedActive || started != nil {
+		t.Fatalf("repeated finalize after pause active=%d started=%v, want %d and NULL", active, started, pausedActive)
+	}
+
+	// Resuming opens a fresh segment, whose elapsed time is added on top of the
+	// paused total rather than replacing it.
+	if _, _, err := d.SetPausedRuntime(task.ID, false); err != nil {
+		t.Fatal(err)
+	}
+	if _, started, err = d.StartTaskRunSegment(task.ID); err != nil {
+		t.Fatal(err)
+	} else if started == nil {
+		t.Fatal("resume did not open a segment")
+	}
+	if _, err := d.Exec(`UPDATE tasks SET run_segment_started_at=now()-interval '3 seconds' WHERE id=$1`, task.ID); err != nil {
+		t.Fatal(err)
+	}
+	active, started, err = d.FinalizeTaskRunSegment(task.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if active <= pausedActive || started != nil {
+		t.Fatalf("resume finalize active=%d started=%v, want increase and NULL", active, started)
+	}
+
+	// Both terminal status paths fold an open segment and leave no live clock.
+	if _, started, err = d.StartTaskRunSegment(task.ID); err != nil {
+		t.Fatal(err)
+	} else if started == nil {
+		t.Fatal("terminal status setup did not open a segment")
+	}
+	if _, err := d.Exec(`UPDATE tasks SET run_segment_started_at=now()-interval '3 seconds' WHERE id=$1`, task.ID); err != nil {
+		t.Fatal(err)
+	}
+	beforeTerminal := active
+	active, started, err = d.SetStatusRuntime(task.ID, "done")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if active <= beforeTerminal || started != nil {
+		t.Fatalf("SetStatusRuntime terminal active=%d started=%v, want increase and NULL", active, started)
+	}
+
+	if _, _, err = d.SetStatusRuntime(task.ID, "running"); err != nil {
+		t.Fatal(err)
+	}
+	if _, started, err = d.StartTaskRunSegment(task.ID); err != nil {
+		t.Fatal(err)
+	} else if started == nil {
+		t.Fatal("guarded terminal setup did not open a segment")
+	}
+	if _, err := d.Exec(`UPDATE tasks SET run_segment_started_at=now()-interval '3 seconds' WHERE id=$1`, task.ID); err != nil {
+		t.Fatal(err)
+	}
+	beforeGuarded := active
+	active, started, won, err := d.SetTerminalStatusGuardedRuntime(task.ID, "failed")
+	if err != nil || !won {
+		t.Fatalf("SetTerminalStatusGuardedRuntime: active=%d started=%v won=%v err=%v", active, started, won, err)
+	}
+	if active <= beforeGuarded || started != nil {
+		t.Fatalf("guarded terminal active=%d started=%v, want increase and NULL", active, started)
+	}
+	finalActive := active
+	active, started, won, err = d.SetTerminalStatusGuardedRuntime(task.ID, "timeout")
+	if err != nil || won {
+		t.Fatalf("second guarded terminal: active=%d started=%v won=%v err=%v", active, started, won, err)
+	}
+	if active != finalActive || started != nil {
+		t.Fatalf("second guarded terminal returned active=%d started=%v, want unchanged active=%d and NULL segment", active, started, finalActive)
+	}
+	got, err := d.GetTask(task.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got == nil || got.ActiveRunSeconds != finalActive || got.RunSegmentStartedAt != nil {
+		t.Fatalf("persisted terminal runtime=%+v, want active=%d and NULL segment", got, finalActive)
+	}
+}
+
+func TestClearOpenTaskRunSegmentsPreservesAccumulatedRuntime(t *testing.T) {
+	d, err := Open(testDSN(t))
+	if err != nil {
+		t.Skipf("postgres unavailable (%v) — skipping", err)
+	}
+	defer d.Close()
+
+	task, err := d.CreateTask("runtime restart clear", "runtime restart clear test", nil, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = d.DeleteTask(task.ID) })
+	if _, err := d.Exec(`UPDATE tasks SET active_run_seconds=17, run_segment_started_at=now()-interval '1 hour' WHERE id=$1`, task.ID); err != nil {
+		t.Fatal(err)
+	}
+
+	cleared, err := d.ClearOpenTaskRunSegments()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cleared < 1 {
+		t.Fatalf("ClearOpenTaskRunSegments cleared %d rows, want at least 1", cleared)
+	}
+	var active int64
+	var started sql.NullTime
+	if err := d.QueryRow(`SELECT active_run_seconds, run_segment_started_at FROM tasks WHERE id=$1`, task.ID).Scan(&active, &started); err != nil {
+		t.Fatal(err)
+	}
+	if active != 17 || started.Valid {
+		t.Fatalf("restart clear changed runtime: active=%d started=%v, want 17 and NULL", active, started)
+	}
+}
diff --git a/db/tasks.go b/db/tasks.go
index 330a4cd..ac5c19e 100644
--- a/db/tasks.go
+++ b/db/tasks.go
@@ -495,10 +495,29 @@ func (d *DB) GetTask(id int64) (*Task, error) {
 
 // SetPaused persists a task's paused flag.
 func (d *DB) SetPaused(id int64, paused bool) error {
-	_, err := d.Exec(`UPDATE tasks SET paused=$1 WHERE id=$2`, paused, id)
+	_, _, err := d.SetPausedRuntime(id, paused)
 	return err
 }
 
+// SetPausedRuntime persists a task's paused flag and, when pausing, folds any
+// open execution segment into active_run_seconds. Keeping this in the DB helper
+// makes direct callers safe even when they do not go through Manager pause
+// orchestration.
+func (d *DB) SetPausedRuntime(id int64, paused bool) (int64, *time.Time, error) {
+	var active int64
+	var started *time.Time
+	err := d.QueryRow(`UPDATE tasks
+SET paused=$1,
+    active_run_seconds=active_run_seconds + CASE WHEN $1 AND run_segment_started_at IS NOT NULL THEN GREATEST(0, FLOOR(EXTRACT(EPOCH FROM (now() - run_segment_started_at)))::bigint) ELSE 0 END,
+    run_segment_started_at=CASE WHEN $1 THEN NULL ELSE run_segment_started_at END
+WHERE id=$2
+RETURNING active_run_seconds, run_segment_started_at`, paused, id).Scan(&active, &started)
+	if err == sql.ErrNoRows {
+		return 0, nil, nil
+	}
+	return active, started, err
+}
+
 // StartTaskRunSegment begins the currently active execution segment. It is
 // idempotent and refuses to start while a task is paused or waiting in the
 // concurrency queue.
@@ -581,14 +600,27 @@ func (d *DB) SetQueued(id int64, queued bool) error {
 // stable); moving back to a non-terminal state clears it, so a re-run has no stale
 // finish time.
 func (d *DB) SetStatus(id int64, status string) error {
-	_, err := d.Exec(`
+	_, _, err := d.SetStatusRuntime(id, status)
+	return err
+}
+
+// SetStatusRuntime updates a task status and returns the committed runtime
+// fields from the same UPDATE. Terminal transitions finalize any open segment.
+func (d *DB) SetStatusRuntime(id int64, status string) (int64, *time.Time, error) {
+	var active int64
+	var started *time.Time
+	err := d.QueryRow(`
 UPDATE tasks
    SET status = $1,
        completed_at = CASE WHEN $1 IN ('done','failed','timeout') THEN COALESCE(completed_at, now()) ELSE NULL END,
        active_run_seconds = active_run_seconds + CASE WHEN $1 IN ('done','failed','timeout') AND run_segment_started_at IS NOT NULL THEN GREATEST(0, FLOOR(EXTRACT(EPOCH FROM (now() - run_segment_started_at)))::bigint) ELSE 0 END,
        run_segment_started_at = CASE WHEN $1 IN ('done','failed','timeout') THEN NULL ELSE run_segment_started_at END
- WHERE id = $2`, status, id)
-	return err
+ WHERE id = $2
+ RETURNING active_run_seconds, run_segment_started_at`, status, id).Scan(&active, &started)
+	if err == sql.ErrNoRows {
+		return 0, nil, nil
+	}
+	return active, started, err
 }
 
 // SetTerminalStatusGuarded sets a terminal status only when the task is NOT already
@@ -596,18 +628,43 @@ UPDATE tasks
 // Returns won=false (no error) when another terminal status already stuck — the
 // caller then leaves it alone. Non-terminal transitions / re-run still use SetStatus.
 func (d *DB) SetTerminalStatusGuarded(id int64, status string) (won bool, err error) {
-	res, err := d.Exec(`
+	_, _, won, err = d.SetTerminalStatusGuardedRuntime(id, status)
+	return won, err
+}
+
+// SetTerminalStatusGuardedRuntime is the runtime-returning form used by the
+// Manager so it can mirror the terminal clock before any follow-up hydration.
+func (d *DB) SetTerminalStatusGuardedRuntime(id int64, status string) (active int64, started *time.Time, won bool, err error) {
+	err = d.QueryRow(`
 UPDATE tasks
    SET status = $1,
        completed_at = COALESCE(completed_at, now()),
        active_run_seconds = active_run_seconds + CASE WHEN run_segment_started_at IS NOT NULL THEN GREATEST(0, FLOOR(EXTRACT(EPOCH FROM (now() - run_segment_started_at)))::bigint) ELSE 0 END,
        run_segment_started_at = NULL
- WHERE id = $2 AND status NOT IN ('done','failed','timeout')`, status, id)
-	if err != nil {
-		return false, err
+ WHERE id = $2 AND status NOT IN ('done','failed','timeout')
+ RETURNING active_run_seconds, run_segment_started_at`, status, id).Scan(&active, &started)
+	if err == sql.ErrNoRows {
+		// Preserve the authoritative runtime fields for the losing terminal
+		// writer. The guarded transition itself is still a no-op.
+		err = d.QueryRow(`SELECT active_run_seconds, run_segment_started_at FROM tasks WHERE id=$1`, id).Scan(&active, &started)
+		if err == sql.ErrNoRows {
+			return 0, nil, false, nil
+		}
+		return active, started, false, err
 	}
-	n, _ := res.RowsAffected()
-	return n > 0, nil
+	return active, started, err == nil, err
+}
+
+// ClearOpenTaskRunSegments drops execution segments that were live when the
+// process stopped. Their wall time is unknowable after a crash or deploy, so
+// startup deliberately begins with no live segment; the engine starts a fresh
+// segment only when it actually resumes work.
+func (d *DB) ClearOpenTaskRunSegments() (int64, error) {
+	res, err := d.Exec(`UPDATE tasks SET run_segment_started_at=NULL WHERE run_segment_started_at IS NOT NULL`)
+	if err != nil {
+		return 0, err
+	}
+	return res.RowsAffected()
 }
 
 // StampFirstRun records a task's first-real-run moment and computes its absolute
diff --git a/server/manager.go b/server/manager.go
index 9907f49..1aa7b70 100644
--- a/server/manager.go
+++ b/server/manager.go
@@ -532,6 +532,13 @@ func NewManager(dir, proxyAddr string) (*Manager, error) {
 	if err != nil {
 		return nil, err
 	}
+	// A live segment cannot be trusted across a process restart: its end time
+	// could be deployment/crash downtime. Clear it before tasks are restored so
+	// the next engine admission starts a fresh segment at actual execution time.
+	if _, err := pg.ClearOpenTaskRunSegments(); err != nil {
+		_ = pg.Close()
+		return nil, fmt.Errorf("clear stale task run segments: %w", err)
+	}
 	if err := pg.RecoverFindingRetests(); err != nil {
 		pg.Close()
 		return nil, fmt.Errorf("recover finding retests: %w", err)
@@ -1297,13 +1304,16 @@ func (m *Manager) SetTaskPaused(id string, paused bool) error {
 	if err != nil {
 		return err
 	}
-	if err := m.pg.SetPaused(n, paused); err != nil {
+	active, started, err := m.pg.SetPausedRuntime(n, paused)
+	if err != nil {
 		return err
 	}
 	m.mu.Lock()
 	if t := m.tasks[id]; t != nil {
 		t.updateLifecycle(func(state *taskLifecycleState) {
 			state.Paused = paused
+			state.ActiveRunSeconds = active
+			state.RunSegmentStartedAt = unixOrZero(started)
 		})
 	}
 	m.mu.Unlock()
@@ -1662,23 +1672,30 @@ func (m *Manager) SetTaskStatusGuarded(id, status string) (won bool, err error)
 	if err != nil {
 		return false, err
 	}
-	won, err = m.pg.SetTerminalStatusGuarded(n, status)
+	active, started, won, err := m.pg.SetTerminalStatusGuardedRuntime(n, status)
 	if err != nil || !won {
 		return won, err
 	}
-	if err := m.syncTaskRuntime(id, n); err != nil {
-		return false, err
-	}
+	// Mirror the committed terminal transition before any optional hydration.
+	// This keeps the in-memory clock stopped even if GetTask later fails.
 	m.mu.Lock()
 	if t := m.tasks[id]; t != nil {
 		t.updateLifecycle(func(state *taskLifecycleState) {
 			state.Status = status
-			if state.CompletedAt == 0 {
-				state.CompletedAt = time.Now().Unix()
+			state.ActiveRunSeconds = active
+			state.RunSegmentStartedAt = unixOrZero(started)
+			if pgdb.IsTerminal(status) {
+				state.RunSegmentStartedAt = 0
+				if state.CompletedAt == 0 {
+					state.CompletedAt = time.Now().Unix()
+				}
 			}
 		})
 	}
 	m.mu.Unlock()
+	if err := m.syncTaskRuntime(id, n); err != nil {
+		return true, err
+	}
 	return true, nil
 }
 
@@ -1691,19 +1708,20 @@ func (m *Manager) SetTaskStatus(id, status string) error {
 	if err != nil {
 		return err
 	}
-	if err := m.pg.SetStatus(n, status); err != nil {
-		return err
-	}
-	if err := m.syncTaskRuntime(id, n); err != nil {
+	active, started, err := m.pg.SetStatusRuntime(n, status)
+	if err != nil {
 		return err
 	}
+	// Mirror the successful UPDATE immediately. A later GetTask hydration is
+	// best-effort and must not reopen a terminal clock in memory.
 	m.mu.Lock()
 	if t := m.tasks[id]; t != nil {
 		t.updateLifecycle(func(state *taskLifecycleState) {
 			state.Status = status
-			// Mirror the DB's completed_at stamp on the live handle so the DTO shows
-			// the finish time without a reload (terminal -> stamp once; else clear).
+			state.ActiveRunSeconds = active
+			state.RunSegmentStartedAt = unixOrZero(started)
 			if pgdb.IsTerminal(status) {
+				state.RunSegmentStartedAt = 0
 				if state.CompletedAt == 0 {
 					state.CompletedAt = time.Now().Unix()
 				}
@@ -1713,6 +1731,9 @@ func (m *Manager) SetTaskStatus(id, status string) error {
 		})
 	}
 	m.mu.Unlock()
+	if err := m.syncTaskRuntime(id, n); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/web/src/app/(main)/function/tasks/page.tsx b/web/src/app/(main)/function/tasks/page.tsx
index fedf22b..df88c10 100644
--- a/web/src/app/(main)/function/tasks/page.tsx
+++ b/web/src/app/(main)/function/tasks/page.tsx
@@ -191,7 +191,7 @@ function fmtDuration(sec: number): string {
 // taskDuration counts only active execution segments. A live segment ticks locally;
 // paused, queued, and terminal tasks stay fixed at their persisted active total.
 function taskDuration(task: Task, nowSec: number): number {
-  const active = Math.max(0, Math.floor(task.active_run_seconds ?? task.run_seconds ?? 0));
+  const active = Math.max(0, Math.floor(task.active_run_seconds ?? 0));
   const segmentStart = task.run_segment_started_unix ?? 0;
   if (task.status === "running" && !task.paused && !task.queued && segmentStart > 0) {
     return active + Math.max(0, Math.floor(nowSec - segmentStart));